The present invention relates to free spinning laminated nuts utilizing laminations of hex shaped hardened coned-disc springs, having a central opening tapped to match threads on an associated bolt. Such nuts have stacked aligned multiple discs retained by a steel outer hex shaped cage. The wrenching dimensions are preferably selected to conform to standard SAE-Metric sizes. Examples of such laminated nut structures are shown and discussed in U.S. Pat. No. 4,383,787, issued to Reynolds on May 17, 1983.
The noted laminated nuts are free running on the bolt until seated. A locking force between the nut and bolt results from the application of additional torque and rotation after initial seating. The additional torque compresses and partially flattens the conical spring discs whereby a mechanical interference occurs between the thread flanks of the nut and bolt; it is believed that this is at least partially due to the change in hole size of the nut as the conical discs flatten. The resultant thread interference and retained spring load between thread flanks resists unloading that might otherwise occur as a result of tensile or vibrational loads. Thus, the independently loaded conical spring threaded segments when flattened create a thread interference that tends to lock the nut against rotation or loosening when subject to such loads.
Since the above noted locking action occurs when the laminated nut is applied in one direction, the nut must be correctly oriented onto the associated bolt to assure proper installation. Thus it would be desirable to provide means to inhibit a reverse or incorrect orientation of the nut on to the bolt so as to assure proper installation, whether such installation is done manually or with automatic feed and installation equipment.
In the present invention radial protrusions are formed at one end of the cage such as to provide a means for detecting the appropriate end of the nut to be gripped by a wrench and thus to inhibit improper orientation and installation on the associated bolt.
Therefore it is an object of the present invention to provide an improved laminated nut structure having means on the cage to inhibit a reverse or incorrect orientation and hence improper installation of the nut on to its associated bolt.